Corrosion resistant cermet wear parts

Abstract

A corrosion resistant cermet comprises a ceramic component (e.g., WC) and a binder alloy comprised of a major component (e.g., one or more of iron, nickel, cobalt, their mixtures, and their alloys) and at least one additive component (e.g., one or more of ruthenium, rhodium, palladium, osmium, iridium, and platinum). Plungers for hyper compressors used in the corrosive environments generated during the manufacture of low density polyethylene (LDPE) or ethylene copolymers are an example of the use of the corrosion resistant cermet.

What is claimed is: 
     
       1. A hyper compressor for high pressure radical polymerization comprising: an elongated body having   (a) a first end;   (b) a second end, wherein the second end further comprises an attachment which facilitates the reciprocation of the elongated body within a portion of the hyper compressor; and   (c) a surface extending between the first end and the second end, wherein at least a portion of the surface engages seals of a seal assembly contained within a portion of the hyper compressor and comprises a corrosion and wear resistant cermet composition comprising: (i) tungsten carbide and   (ii) between about 6-19% by weight binder alloy comprising cobalt and between about 26-60% by weight ruthenium,     wherein the combination of the cobalt and ruthenium imparts improved corrosion resistance in acid/water solutions comprised of at least one of formic acid, acetic acid, methacrylic acid, maleic acid, sulfuric acid, nitric acid, and hydrochloric acid; sea water; or a hydrazine mono-hydrate/water solution.   
     
     
       2. A hyper compressor for high pressure polymerization comprising an elongated body having: (a) a first end;   (b) a second end, wherein the second end further comprises an attachment which facilitates the reciprocation of the elongated body within a portion of the hyper compressor; and   (c) a surface extending between the first end and the second end, wherein at least a portion of the surface engages seals of a seal assembly contained within a portion of the hyper compressor and comprises a corrosion and wear resistant cermet composition comprising: (i) at least one ceramic component comprised of at least one of boride, carbide, nitride, oxide, silicide, their mixtures, their solutions, and combinations thereof; and   ii) between about 6-19% by weight binder alloy comprised of a major component comprising one or more of iron, nickel, cobalt, their mixtures, and their alloys and an additive component comprising between about 26-60% by weight of the binder alloy and at least one of ruthenium, rhodium, palladium, osmium, iridium, platinum, their alloy, and mixtures thereof, wherein the additive component imparts corrosion resistance against at least one of acids, bases, salts, lubricants, gasses, silicates, or any combination of the preceding to the corrosion and wear resistant cermet composition.     
     
     
       3. The hyper compressor according to claim 2, wherein the additive component of the corrosion and wear resistant cermet composition comprises between about 26-34% by weight of the binder alloy. 
     
     
       4. The hyper compressor according to claim 3, wherein the binder alloy of the corrosion and wear resistant cermet composition comprises between about 8-17% by weight of the corrosion and wear resistant cermet composition. 
     
     
       5. The hyper compressor according to claim 2, wherein the at least one ceramic component of the corrosion and wear resistant cermet composition comprises at least one carbide of one or more of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W. 
     
     
       6. The hyper compressor according to claim 5, wherein said at least one carbide of the corrosion and wear resistant cermet composition comprises tungsten carbide. 
     
     
       7. The hyper compressor according to claim 6, wherein the at least one ceramic component of the corrosion and wear resistant cermet composition further comprises at least one carbide of one or more of Ti, Nb, and Ta. 
     
     
       8. The hyper compressor according to claim 6, wherein the corrosion and wear resistant cermet composition comprises a ruthenium-cobalt or a ruthenium-cobalt-tungsten cemented tungsten carbide which is resistant to solutions of water and at least one of formic acid, acetic acid, maleic acid, and methacrylic acid. 
     
     
       9. The hyper compressor according to claim 8, wherein a corrosion rate of the corrosion and wear resistant cermet composition after about seven (7) days at about 50° C. (122° F.) is not greater than about 300 m.d.d. in a one (1)% organic acid/water solution. 
     
     
       10. The hyper compressor according to claim 6, wherein the corrosion and wear resistant cermet composition comprises a ruthenium-cobalt or a ruthenium-cobalt-tungsten cemented tungsten carbide which is resistant to solutions of water and at least one of sulfuric acid, nitric acid, hydrochloric acid, salt, and hydrazine mono-hydrate. 
     
     
       11. The hyper compressor according to claim 10, wherein a corrosion rate of the corrosion and wear resistant cermet composition after about seven (7) days at about 65° C. (149° F.) is not greater than about 80 m.d.d. in five (5)% mineral acid/water solutions. 
     
     
       12. The hyper compressor according to claim 2, wherein the additive component of the corrosion and wear resistant cermet composition comprises ruthenium comprising about 26-40% by weight of the binder alloy. 
     
     
       13. The hyper compressor according to claim 12, wherein the binder alloy of the corrosion and wear resistant cermet composition comprises between about 8-17% by weight of the corrosion and wear resistant cermet composition. 
     
     
       14. A hyper compressor for high pressure polymerization comprising an elongated body having: (a) a first end;   (b) a second end, wherein the second end further comprises an attachment which facilitates the reciprocation of the elongated body within a portion of the hyper compressor; and   (c) a surface extending between the first end and the second end, wherein at least a portion of the surface engages seals of a seal assembly contained within a portion of the hyper compressor and the at least a portion comprises a corrosion and wear resistant cermet composition comprising: (i) tungsten carbide and   (ii) between about 6-19% by weight binder alloy comprising cobalt and between about 26-60% by weight ruthenium,     wherein the combination of the cobalt and ruthenium imparts improved corrosion resistance in acid/water solutions comprised of at least one of formic acid, acetic acid, methacrylic acid, and maleic acid   wherein the corrosion and wear resistant cermet composition has:   a Rockwell A hardness of at least about 85;   a transverse rupture strength of at least about 1.7 GPa (250 ksi); and   a corrosion rate after about seven (7) days at about 50° C. (122° F.) in a one (1)% acid/water solutions comprised of at least one of formic acid, acetic acid, methacrylic acid, and maleic acid of not greater than about 120 m.d.d.   
     
     
       15. The hyper compressor according to claim 14, wherein ruthenium comprises at most 40% of the binder alloy of the corrosion and wear resistant cermet composition. 
     
     
       16. The hyper compressor according to claim 14, wherein the binder alloy comprises between 8-17% of the cermet, ruthenium comprises at most 40% of the binder alloy, the transverse rupture strength is at least 2.8 GPa (310 ksi), and the corrosion rates are no greater than 80 m.d.d. 
     
     
       17. The hyper compressor according to claim 14, wherein substantially all of the elongated body comprises the corrosion and wear resistant cermet composition. 
     
     
       18. The hyper compressor according to claim 14, wherein the Rockwell A hardness of the corrosion and wear resistant cermet composition is up to about 92. 
     
     
       19. The hyper compressor according to claim 14, wherein the tungsten carbide further comprises at least one carbide of one or more of Ti, Nb, and Ta. 
     
     
       20. The hyper compressor according claim 14, wherein the binder alloy comprises between about 8-17% by weight of the corrosion and wear resistant cermet composition. 
     
     
       21. The hyper compressor according to claim 14, wherein the additive component comprises between about 26-34% by weight of the binder alloy. 
     
     
       22. A hyper compressor for high pressure polymerization comprising an elongated body having: (a) a first end;   (b) a second end, wherein the second end further comprises an attachment which facilitates the reciprocation of the elongated body within a portion of the hyper compressor; and   (c) a surface extending between the first end and the second end, wherein at least a portion of the surface engages seals of a seal assembly contained within a portion of the hyper compressor and the at least a portion comprises a corrosion and wear resistant cermet composition comprising: (i) tungsten carbide and   (ii) between about 6-19% by weight binder alloy comprising cobalt and between about 26-60% by weight ruthenium,     wherein the combination of the cobalt and ruthenium imparts improved corrosion resistance in acid/water solutions comprised of at least one of sulfuric acid, nitric acid, and hydrochloric acid; sea water; or hydrazine mono-hydrate/water solutions   wherein the corrosion and wear resistant cermet composition has:   a Rockwell A hardness of at least about 85;   a transverse rupture strength of at least about 1.7 GPa (250 ksi); and   a corrosion rate after about seven (7) days at about 65° C. (149° F.) in: a five (5)% acid/water solution comprised of at least one of sulfuric acid and nitric acid;   a 37% hydrochloric acid/water solution;   synthetic sea water; or   98% hydrazine mono-hydrate/water solution of not greater than about 80 m.d.d.     
     
     
       23. The corrosion and wear resistant cermet composition according to claim 22, wherein the ruthenium comprises between about 26-40% of the binder alloy. 
     
     
       24. The hyper compressor according to claim 23, wherein the binder alloy comprises between about 8-17% by weight of the corrosion and wear resistant cermet composition. 
     
     
       25. The hyper compressor according to claim 22, wherein the binder alloy comprises between 8-17% of the cermet, the transverse rupture strength is at least 2.8 GPa (310 ksi), and the corrosion rates are no greater than 80 m.d.d. 
     
     
       26. The hyper compressor according to claim 22, wherein substantially all of the elongated body comprises the corrosion and wear resistant cermet composition. 
     
     
       27. The hyper compressor according to claim 22, wherein the binder alloy comprises between about 8-17% by weight of the corrosion and wear resistant cermet composition. 
     
     
       28. The hyper compressor according to claim 22, wherein the additive component comprises between about 26-34% by weight of the binder alloy.